Of particular interest to the present invention is the treatment of heart valve disease. There are two major categories of heart valve disease: (i) stenosis, which is an obstruction to forward blood flow caused by a heart valve, and (ii) regurgitation, which is the retrograde leakage of blood through a heart valve. Stenosis often results from calcification of a heart valve that makes the valve stiffer and less able to open fully. Therefore, blood must be pumped through a smaller opening. Regurgitation can be caused by the insufficiency of any of the valve leaflets such that the valve does not fully close.
In the past, repairing or replacing a malfunctioning heart valve within a patient has been achieved with a major open-heart surgical procedure, requiring general anesthesia and full cardiopulmonary by-pass. This requires complete cessation of cardiopulmonary activity. While the use of extracorporeal cardiopulmonary by-pass for cardiac support is a well accepted procedure, such use has often involved invasive surgical procedures (e.g., median sternotomies, or less commonly, thoracotomies). These operations usually require one to two weeks of hospitalization and several months of rehabilitation time for the patient. The average mortality rate with this type of procedure is about five to six percent, and the complication rate is substantially higher.
Endovascular surgical techniques for heart surgery have been under recent development. In contrast to open-heart surgical procedures, endovascular procedures may have a reduced mortality rate, may require only local anesthesia, and may necessitate only a few days of hospitalization. However, the range of procedures that has been developed for an endovascular approach to date has been limited to repair of the coronary arteries, such as angioplasty and atherectomy.
Some progress has been made in the development of endovascular heart valve procedures. For example, for patients with severe stenotic valve disease who are too compromised to tolerate open-heart surgery to replace the heart valve as described above, surgeons have attempted endovascular balloon aortic or mitral valvuloplasty. These procedures involve endovascularly advancing a balloon dilatation catheter into the patient's vasculature until the balloon of the catheter is positioned between the valve leaflets. Then the balloon is inflated to either: (i) split the commissures in a diseased valve with commissural fusion, or (ii) crack calcific plaques in a calcified stenotic valve. However, this method may only provide partial and temporary relief for a patient with a stenotic valve. Instances of restenosis and mortality following balloon aortic valvuloplasty have led to virtual abandonment of this procedure as a treatment for a diseased aortic valve.
Endovascular procedures for valve implantation inside a native and diseased valve have been explored. A catheter-mounted valve is incorporated into a collapsible cylindrical structure, such as a stent (commonly referred to as a “valved stent”). In these procedures, an elongated catheter is used to insert a mechanical valve into the lumen of the aorta via entry through a distal artery (e.g., the femoral or brachial artery). Such procedures have been attempted on selective, terminally ill patients as a means of temporarily relieving the symptoms of a diseased valve.
The percutaneous placement of an artificial valve may have certain limitations and ancillary effects. For example, at present, such procedures are only of benefit to a small number of patients and are not meant to become an alternative to surgical heart valve procedures requiring the use of extracorporeal bypass. Another issue is that performing the entire procedure via small diameter vessels (e.g., the femoral, iliac or brachial arteries) restricts the use of larger tools and devices for the resection or repair of the diseased heart valve. Furthermore, this endovascular procedure may increase the risk of various vascular complications such as bleeding, dissection, rupture of the blood vessel, and ischemia to the extremity supplied by the vessel used to perform the operation.
Moreover, in some cases, one or more of a patient's femoral arteries, femoral veins, or other vessels for arterial and venous access may not be available for introduction of delivery devices or valve removal tools due to inadequate vessel diameter, vessel stenosis, vascular injury, or other conditions. In such cases, there may not be sufficient arterial and venous access to permit the contemporaneous use of the necessary interventional devices (e.g., an angioplasty catheter, atherectomy catheter, or other device) for a single surgical procedure. Therefore, unless alternate arterial or venous access for one or more of these catheters can be found, the procedure cannot be performed using endovascular techniques.
Another possible disadvantage of the small vessel procedure is that the new valve must be collapsed to a very small diameter that could result in structural damage to the new valve. Additionally, such remote access sites like the femoral artery may make precise manipulation of the surgical tools more difficult (e.g., exchange of guide wires and catheters and deployment of the new valve). Furthermore, placing wires, catheters, procedural tools, or delivery devices through one or more heart structures (e.g., the mitral valve) to reach the target site can result in damage to those structures (e.g., acute malfunctioning or insufficiency of the valve being mechanically hindered by the surgical equipment or valve deterioration resulting from mechanical friction inflicting micro-lesions on the valve).
Also to be considered in connection with such procedures is the potential of obstructing the coronary ostia. The known percutaneous procedures for implanting heart valves do not have a safety mechanism to ensure proper orientation of the new valve. Therefore, there is a possibility that the deployed valve will obstruct the coronary ostia, which can result in myocardial ischemia, myocardial infarction, and eventually the patient's death.
These procedures leave the old valve in place, and the new valve is implanted within the diseased valve after the diseased valve has been compressed by a balloon or other mechanical device. Therefore, there may be a possibility of embolic stoke or embolic ischemia from valve or vascular wall debris that is liberated into the blood flow as the diseased valve is dilated and compressed. Furthermore, a rim of diseased tissue (e.g., the compressed native valve) decreases the diameter and cross-sectional surface of the implanted valve, potentially under-treating the patient and leading to only partial relief of his symptoms.
It would therefore be desirable to develop systems and methods for satisfactorily performing various cardiovascular procedures, particularly procedures for heart valve placement or removal and replacement, which do not require the use of an extracorporeal bypass or invasive surgical procedure, such as a sternotomy. It would be further desirable to perform such procedures through very small incisions in the patient (e.g., via several small thoracotomies). The devices and methods will preferably facilitate the access, resection, repair, implantation, and/or replacement of the diseased cardiac structure (e.g., one or more diseased heart valves). The devices and methods should preferably minimize the number of arterial and venous penetrations required during the closed-chest procedures, and desirably, should require no more than one cardiac and one femoral arterial penetration. The present invention satisfies these and other needs.
The descriptive terms antegrade and retrograde mean in the direction of blood flow and opposite the direction of blood flow, respectively, when used herein in relation to the patient's vasculature. In the arterial system, antegrade refers to the downstream direction (i.e., the same direction as the physiological blood flow), while retrograde refers to the upstream direction (i.e., opposite the direction of the physiological blood flow). The terms proximal and distal, when used herein in relation to instruments used in the procedure, refer to directions closer to and farther away from the heart, respectively. The term replacement normally signifies removal of the diseased valve and implantation of a new valve. However, a new valve may also be implanted directly over top of a diseased valve. An implantation procedure would be the same as a replacement procedure without the removal of the diseased valve.